Nikolaus Schwaiger

Formation of liquid and solid products from liquid phase pyrolysis

The aim of the present work was to improve the C:O ratio in biomass by preserving the lignin macrostructure of lignocellulosic feed. The intention of liquid phase pyrolysis is to liquefy biomass and prepare biomass for further upgrading steps like hydrogenation and deoxygenation. Pyrolysis was carried out in a non-aqueous liquid phase heat carrier. The process was carried out in a semi-batch reaction vessel under isothermal conditions at T=350°C, supported by a quench to stop reactions instantaneously in order to observe formation of solid intermediates. This pyrolysis system enables the observation of liquid and solid product formation. Transformation of biomass into biochar was analyzed by infrared spectroscopy and elemental analysis. Stable lignin structure throughout the whole transformation was confirmed. It was shown that the lignin frame in wood remains without substantial loss, while the major amount of carbohydrates is pyrolyzed during liquid phase pyrolysis at T=350°C.

Liquefaction of pyrolysis derived biochar: a new step towards biofuel from renewable resources

There are several ways to produce the renewable resource biochar, such as pyrolysis or hydrothermal carbonization. Technologies for the conversion of biochar to biofuels could contribute to suffice the growing demand for fuel. Liquid-phase pyrolysis produces about 40 wt% of biochar. Direct liquefaction of biochar is a conceivable way of producing biofuels but has not been considered yet. Direct liquefaction of biochar is carried out in a 450 ml batch reactor at the temperature of 425 °C using tetralin as a hydrogen donor solvent. Several experiments were conducted to investigate the influence of an initial heating and an isothermal stage on the conversion of biochar to biofuel. The isothermal stage was investigated at two pressure levels. Reaction time was limited to 30 min. Biochar conversion of 84% and an oil yield of 72% were observed.

Biofuels from liquid phase pyrolysis oil: a two-step hydrodeoxygenation (HDO) process

New biomass utilization technologies and concepts are needed to suffice future increasing energy demand. This paper contributes to the understanding of liquid phase pyrolysis (LPP) oil upgrading, which significantly differs from fast pyrolysis (FP) oil upgrading processes. A two-step hydrodeoxygenation (HDO) process was established to convert the LPP oil into a biofuel with diesel fuel-like properties. In the first HDO step (250 °C, 85 bar), the bulk of the water and most of the highly-oxygenated water-soluble carbonaceous constituents were removed, to lower hydrogen consumption in the second HDO step. In addition, the highly reactive compounds were stabilized in the first step. In the second HDO step (400 °C, 150/170 bar), the product specification was improved. This paper shows a proof-of-principle for a two-step HDO process for converting LPP oil to a diesel-like biofuel.

Chemical loop systems for biochar liquefaction: hydrogenation of Naphthalene

Liquefaction of biochar from liquid-phase pyrolysis was carried out in the solvent Tetralin. Tetralin is able to act as hydrogen donor during liquefaction of biochar and is itself rearranged into Naphthalene. Naphthalene must be re-hydrogenated to Tetralin to allow for further use in the liquefaction reaction (chemical loop system). Therefore Naphthalene hydrogenation was investigated, applying a full factorial design of experiments approach. The yield of Tetralin was chosen as response variable, while two-level-factors for temperature (150 °C and 200 °C), pressure (20 bar and 50 bar) and Raney-Nickel catalyst load (5 wt% and 10 wt%) were selected. The Design of Experiments approach showed a rising influence of all three factors in the order: temperature < pressure < catalyst load. The reaction kinetics of the hydrogenation of Naphthalene to Tetralin and Decalin was then investigated at 150 °C and 200 °C. The reaction proceeds stepwise and not in consecutive steps. In a first step Naphthalene reacts selectively with 96% yield to Tetralin, while the reaction of Tetralin to Decalin does not start until all Naphthalene is consumed. The rate-constant of the reaction of Naphthalene to Tetralin is one magnitude higher than that for the reaction of Naphthalene to Decalin. This is in agreement with the findings from the design of experiments approach. The results of these investigations indicate that the chemical-loop system Naphthalene–Tetralin is suitable for usage in the liquefaction of biochar.

Diesel production from lignocellulosic feed: the bioCRACK process

The bioCRACK process is a promising technology for the production of second generation biofuels. During this process, biomass is pyrolized in vacuum gas oil and converted into gaseous, liquid and solid products. In cooperation with the Graz University of Technology, the liquid phase pyrolysis process was investigated by BDI – BioEnergy International AG at an industrial pilot plant, fully integrated in the OMV refinery in Vienna/Schwechat. The influence of various biogenous feedstocks and the influence of the temperature on the product distribution in the temperature range of 350°C to 390°C was studied. It was shown that the temperature has a major impact on the product formation. With rising temperature, the fraction of liquid products, namely liquid CHO-products, reaction water and hydrocarbons, increases and the fraction of biochar decreases. At 390°C, 39.8 wt% of biogenous carbon was transferred into a crude hydrocarbon fractions. The type of lignocellulosic feedstock has a minor impact on the process. The biomass liquefaction concept of the bioCRACK process was in pilot scale compatible with oil refinery processes.

Biogene Treibstoffe aus Biomassepyrolyse

The bioCRACK process can convert as much as 18 percent of biomass into fuel intermediates for diesel production. This process was operated in pilot scale over two years. Beside fuel intermediates, pyrolysis oil is formed in the bioCRACK process. In the second technology development step pyrolysis oil was upgraded by continuous hydrodeoxygenation in lab scale. Results show a carbon yield from pyrolysis oil of 50 percent. The boiling range of upgraded pyrolysis oil is between diesel and gasoline.

Lignocellulosic Biofuels: Phase Separation during Catalytic Hydrodeoxygenation of Liquid Phase Pyrolysis Oil

This paper contributes to the understanding of liquid phase pyrolysis (LPP) oil upgrading. The subject of discussion is hydrodeoxygenation (HDO). A three-stage hydrotreatment of liquid phase pyrolysis oil is described. It was found that during the initial heating stage conditions no HDO oil was produced. The HDO oil was formed during the main heating stage. During the initial heating stage, the oxygen content and the average molecular weight remained relatively constant. In the main heating stage the oxygen content decreased from 40 wt.% to 24 wt.% and the average molecular weight also decreases from 630 to 570 g/mol. Finally in the isothermal stage HDO oil was formed, indicated by a drop in oxygen content.

High-throughput continuous hydrodeoxygenation of liquid phase pyrolysis oil

Hydrodeoxygenation (HDO) of liquid phase pyrolysis oil with high water content was performed continuously in a plug flow reactor on a sulfided CoMo/Al2O3 catalyst under a hydrogen pressure of 120 bar at 400 °C. The intention of this project was to achieve fuels of diesel, kerosene and gasoline quality from liquid phase pyrolysis oil (LPP oil). The liquid hourly space velocity (LHSV) was altered between 0.5 h−1 and 3 h−1. The LHSV was higher than those reported for state-of-the-art HDO processes. The LPP oil was derived from the bioCRACK pilot plant in the OMV refinery in Vienna/Schwechat, which was operated by BDI – BioEnergy International GmbH. After HDO, separation of the upgraded hydrocarbon fraction from the aqueous carrier was achieved. About 50% of the biogenous carbon was transferred into the liquid hydrocarbon product phase, and the residual amount was transferred into the gas phase. Comparably slow catalyst aging by coke formation was attributed to the high water content of LPP oil. During HDO, a fuel of almost gasoline and diesel quality was produced. The H/C ratio was between 1.7 and 2 with a residual oxygen content of 0.0 wt% to 1.2 wt%. The boiling range of the hydrocarbon product phase was between those of gasoline and diesel. In GC-MS analysis, mainly saturated alkanes were found.

Temperature Dependence of Single Step Hydrodeoxygenation of Liquid Phase Pyrolysis Oil

In this paper, continuous hydrodeoxygenation (HDO) of liquid phase pyrolysis (LPP) oil in lab-scale is discussed. Pyrolysis oil is derived from the bioCRACK pilot plant from BDI - BioEnergy International GmbH at the OMV refinery in Vienna/Schwechat. Three hydrodeoxygenation temperature set points at 350, 375, and 400°C were investigated. Liquid hourly space velocity (LHSV) was 0.5 h−1. Hydrodeoxygenation was performed with an in situ sulfided metal oxide catalyst. During HDO, three product phases were collected. A gaseous phase, an aqueous phase and a hydrocarbon phase. Experiment duration was 36 h at 350 and 375°C and 27.5 h at 400°C in steady state operation mode. Water content of the hydrocarbon phase was reduced to below 0.05 wt.%. The water content of the aqueous phase was between 96.9 and 99.9 wt.%, indicating effective hydrodeoxygenation. The most promising results, concerning the rate of hydrodeoxygenation, were achieved at 400°C. After 36/27.5 h of experiment, catalyst deactivation was observed.